Vehicle power brake mechanism



1968 D. T. AYERS, JR ETAL 3,369,364

VEHICLE POWER BRAKE MECHANISM Filed Feb. 9, 1966 2 Sheets-Sheet l w 13 gJ9 I I...

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Feb. 20, 1968 D. T. AYERS, JR, 'ETAL 3,369,364

VEHICLE POWER BRAKE MECHANISM United States Patent VEHICLE POWER BRAKEMECHANISM David T. Ayers, Jr., Birmingham, and Lawrence E.

Pullrownik, Plymouth, Micl1., assignors to Kelsey- Hayes Company,Romulus, Mich., a corporation of Delaware Filed Feb. 9, 1966, Ser. No.526,153 7 Claims. (Cl. 60--54.5)

ABSTRACT OF THE DISCLOSURE A power braking system for a motor vehicledriven by an internal combustion engine. The braking system includes abooster unit that is actuated in part by the air pressure generated byan air compressor that is driven by an internal combustion engine andwhich aircompressor is used in conjunction with a smog emission reducingsystem of the engine.

This invention relates generally to vehicle power brake assemblies, andparticularly to an improved, highly eflicient and compact power brakebooster unit.

In general, power brake booster units employ a diiferential pressureresponsive movable wall operatively connected to the vehicle mastercylinder. The pressure responsive wall is brought into play byapplication of a conventional brake pedal and applies a greater force tothe piston of the master cylinder than the manual force applied to thebrake pedal by the vehicle operator. The resulting pressure developed inthe master cylinder, in turn, pressurizes the brake cylinders at thevehicle wheels to slow or stop the vehicle.

Conventionally, the differential pressure wall includes a diaphragmwhich is exposed on one side thereof to atmospheric pressure and on theother side to either subatmospheric or superatmospheric pressure. In theformer, atmospheric pressure acting on one side of the diaphragm movesit in a direction against the subatmospheric pressure or vacuumcondition on the other side usually supplied by exposing this side ofthe diaphragm to the intake manifold of the vehicle engine. In thelatter, superatmospheric pressure supplied by a pressure pump to oneside of the diaphragm moves it in a direction against atmosphericpressure action on the other side.

In both of these prior cases, the force that a booster unit is capableof delivering is a function of the pressure differential betweenatmospheric pressure and either manifold vacuum or the pressuredeveloped by a pressure pump and the area of the diaphragm. To produce abooster unit of the prior type having a high output capacity, it isnecessary to use a diaphragm having a large diameter or to employ abooster having multiple diaphragms. Increasing the diameter of thediaphragm may be impossible in view of the available space, and bothexpedients increase the cost of the unit materially. Furthermore,multiple diaphragm boosters are relatively complex in nature.

An important object of the present invention, therefore, is to providean improved relatively small, compact and inexpensive power brakebooster unit assembly having a high output capability.

Further objects of the present invention are to provide a booster unitassembly of the above character which, overall, is relativelyinexpensive tomanufacture, simple and durable in construction andreliable and eflicicnt in use.

Other objects and advantages of the present invention will become moreapparent from the following detailed description taken in conjunctionwith the drawings in which:

3,369,364 Patented Feb. 20, 1968 ice FIGURE 1 is a view illustrating inelevation a typical automotive vehicle engine and showingdiagrammatically a typical installation of a power brake booster unitassembly constructed according to the present invention;

FIG. 2 is a sectional view of FIG. 3 taken along the line 2-2 thereofand illustrating the booster unit; and

FIG. 3 is a sectional view of FIG 2 taken along the line 33 thereof.

Broadly described, the present invention includes a booster unit havinga pressure responsive movable wall therein having one side exposed to asubatmospheric pressure, normally open bypass means subjecting bothsides of said wall to said subatmospheric pressure, normally closedvalve means adapted, when opened, to connect the other side of saidwallto a superatmospheric pressure, actuating means op'eratively associatedwith said pressure responsive wall and adapted when moved in onedirection to close said bypass means and open said valve means.

Referring now more specifically to the drawings, a power brake boosterunit, illustrated generally at 11 in FIG. 1, is seen to include ahousing 13 connected by a pair of conduits 15, 17 to a source of vacuumor subatmospheric pressure, such as the intake manifold 19 of anautomotive internal combustion engine 21 and to a source ofsuperatmospheric pressure, such as an air injector pump 23,respectively. This pump 23 is conveniently connected to a conventionalair filter 24 and may be used, as is the case in a number of modernautomotive engines, to supply air to further oxidize and dilute thegases discharged to the engine exhaust manifold and reduce airpollution. Conveniently, the pump 23 is driven by a belt 25 whichconnects a pair of pulleys 27, 29 mounted on the engine drive shaft 31and the pump 23, respectively.

The booster unit 11 is shown in greater detail in FIGS. 2 and 3 and asseen there, the housing 13 includes a pair of interconnected housingsections 33, 35 having a pressure responsive wall 37 movably disposedtherein. The vacuum conduit 15 is connected to the housing section 33 bya fitting 39 extending through an opening 41 and sealed by a resilientmember 43. The pressure conduit 17 extends through an opening 45 in thehousing section 35 and is connected by a coupling 47 to one end of aflexible conduit loop or pigtail 49, the other end of which is fitted ona tubular projection 51 secured to 01' integral with a piston body 53which forms a part of the pressure responsive wall 37. An annular bead54 on the conduit 17 overlies and seals the opening 45 and is welded tothe housing section 35.

The piston body 53 has an annular seat 55 on which an inner head 57 of arolling diaphragm 59 is positioned and held by a radial flange 60 andthe projection 51. The diaphragm 59 forms a part of the wall 37 and hasan outer head 61 clamped between the two housing sections 33, 35 andtogether with the piston body 53 divides the housing 13 into a constantpressure chamber 63 and a variable pressure chamber 65.

The piston body 53 is connected by screws 67 to a plate 69 from whichdepends a force transmitting rod 71. The outer end of the rod 71 isseated within a plunger 73 slidably disposed in a bore 75 of a mastercylinder unit 77. A reservoir 79 supplies hydraulic fluid to the bore 75through a passage 81 and the plunger 73 is provided with the usual seals83, 85 to generate hydraulic pressure and actuate the vehicle wheelcylinders (not shown) in the usual manner when the plunger 73 is movedtoward the left as seen in FIG. 3. A snap ring 87 prevents the plunger73 from pulling out of the bore 75.

When the parts are at rest as shown in FIG. 3, a vacuum orsubtamospheric pressure condition exists in both of the chambers 63, 65and the pressure responsive means 37 is biased toward the right in anoff position under the force of a bellows spring $9 where a resilientannular seal 83 on the piston body 53 engages an annular flange as onthe housing section 35. The bellows spring 89 has an outer beaded end 91clamped between a flange 93 on the housing section 33 and a radialflange 9 on the master cylinder unit 77 and its inner end @3 is seatedagainst the plate as. The interior of the bellows S9 is exposed toatmospheric pressure through a passage 95 in the master cylinder unit 77and since the chamber 63 is under a vacuum or subatmospheric pressurecondition, the bellows 89 tends to expand and biases the pressureresponsive means 37 to the right. A ring 97 surrounds the bellowslimiting its expansion and a filter 99 prevents dirt, grease and otherforeign matter from getting through the passage and into the bore '75.

A normally open bypass Th1 communicates the chambers 63, 65 so that thepressure responsive means 37 normally is vacuum suspended and is held inthe position illustrated by the bellows spring 39 as described above.Forming the bypass is a generally cyiiii al bore M33 in the piston body53 communicated With the chamber 65 by a radial passage and normallyopen to the chamber 63. A seal ltd? having a thickened inner end N39 ispositioned in a counterbore iii adjacent the bore 1% with the thickenedend M9 normally engaging a tapered lip 113 between the bore Hi3 and thecounterbore l llil. The outer end or the seal i is also thickened as at115 and is held in an enlarged bore 117 adjacent the counterbore ill bya retaining ring 119. A light compression spring 121 between thethickened ends 1%,

An axially slidable piston 1127 is loosely disposed within the bore Th3and is connected at its outer end by a resilient washer 129 to a pushrod 131 which in turn is operatively connected to a conventional brakepedal (not shown) in the usual manner. The piston has a reduced portion133 freely extending through the seal 107 and the rigidifying member 123and is provided with an annular groove 135 adjacent the radial passageres. An axially projecting lip 137 on the piston 1Z7 adjacent thereduced portion 133 is adapted to engage the thickened end N9 of theseal iii? but is normally held spaced therefrom by a compression springcaged between a radially outwardly extending shoulder on the outer endof the piston 127 and a radial shoulder lid?) separating a reduced boreportion and a counterbore in? in the piston body 53. A snap ring 149 ispositioned in the counterbore 147 behind the piston 127 to prevent itfrom pulling out of the piston body 53 and the piston T27 carries anannular seal 15]; which engages the wall of the reduced bore lid-5 toprevent loss of pressure therepast. Thus, with the parts in their normalpositions as shown in FIG. 3, the bypass 01 is open and the vacuum supplied to the chamber 63 through the conduit is comrnunicated to thechamber 65 between the parts which include the seal Th7 and the reducedpiston portion 133, the seal end Th9 and the piston lip 137, the pistonand the bore 163, and from around the piston groove 135 out through theradial passage 1 55. The pressure supplied from the pump 23 to theconduit 17 and thence to the pigtail 4-9 and the tubular projection 51is prevented from reaching the chamber 65 by a valve means 1'53 formedbetween the thickened end iii? of the seal it)? and the tapered lip 113which the end M9 normally en gages. With the parts in this position,both chambers 63, 65 are under a vacuum or subatmospheric pressure andremain so positioned until the brake pedal (not shown) is applied.

When the pedal (not shown) is applied, the push rod 131 moves toward theleft as seen in FIG. 3 as does the piston 127. After a slight movementin this direction, the piston lip 137 engages the thickened seal end andcloses the bypass flit! thereby blocking communication between thechambers s3, 65 whereby only the chamber as continues to be exposed tothe vacuum from the conduit i5. Substantially simultaneously withclosing of the bypass Hill, the valve 153 opens since movement of thepush rod 13; and the piston 127 to the left after the piston lip ll3'7engages the seal end it)? unseats it from the tapered lip 123. At thispoint, superatrnospheric press from the pump 23 flows through the radialpassage i o in the piston body 53 and into the chamber 65. The pressurediiferential now existing between the chambers 6.3, 65 acts on theeffective area of the pressure responsive wall 57 and causes it to movetoward the left under a motivating force substantially greater than thatgencrated by the vehicle operator on the push rod 131. Movement of thepressure responsive wall 37 to the left moves the plunger '73 topressurize the brake cylinders (not shown) and apply the brakes asdescribed above with step-up force ratio which is a function of thepressure diflerential between the constant press re vacuum chamber 63and the variable, now superatmospheric, pressure chamber 65.

In order to provide pedal reaction or feel when the brakes are applied,a lever 155 is positioned adjacent the plate 69 and is pivotally mountedby diametrically spaced trunnions (not shown) for movement about ahorizontal axis near'the bottom of the plate (19. The lower end of thelever 155 is provided with a pair of rearward projections 157 (only oneof which is shown) which engage a r ly inwardly extending flange 159formed on a plate roll secured to the diaphragm 59 and over which thediaphragm rolls during movement of the pressure responsive means 3'7.The piston 1 27 has a resilient bumper T55 positioned in a recess 167 inthe piston inner end and the bumper is provided with an axial projectionE69 engaging another rearward projection 170 on the lever When thepiston iii 1'7 moves toward the left as seen in FIG. 3 to close thebypass Till and open the valve 153 as described above, the diaphragm 59and the plate 161 move toward the left under the pressure differentialin the chambers s3, s5 at a greater rate than that of the piston body53. The flange 159 on the plate lol engages and pivots the lever 1555 ina clockwise direction causing it to act rearwardly or to the right onthe piston 127 through the bumper 1&5. This, in turn, provides the pedalreaction or feel by acting back through the push rod 131 to the brakepedal (not shown) with a force proportional to the differential pressurein the chambers 63, 65. A counteraction compression spring 171 cagedbetween the lever 155 and the rigidifying member 125 normally biases thelever 155 to the off position shown in FlG. 3 but is easily overcome bythe tilting force on the lever 55 provided by the flange 159, thecompression on one side of the spring being greater than on the otherside. A resilient bumper 173 positioned in a recess 175 in the pistonbody 53 engages the flange 159 and maintains it spaced from the pistonbody 53.

When the brake pedal is released, the spring 139 returns the piston?1217 to the illustrated position relative to the piston body 53. Thiscauses the valve 153 to close and the bypass dill to open therebyblocking the flow of pressure from the pump 23 to the chamber 65 andpermitting communication between the chambers 63, 65 so that thepressures therein rapidly equalize. When this oc curs, the bellowsspring 89 returns the pressure responsive unit 37 to the illustratedposition during which time the spring 139 maintains the illustratedrelative positioning of the piston T27 and piston body 53 and the brakesare released.

Should the booster unit l3 fail to operate as described above for anyreason, the brakes will still function since when the push rod 131- andpiston T27 move toward the let-ft, the bumper M5 and the piston E21 movethe lever 1'55 in a reverse pivotal direction from that described aboveor counterclockwise as viewed in FIG. 3. This the left as well as theplunger '73 to apply the brakes so that even with failure of the powerunit, a direct mechanical actuation of the brakes is achieved.

In practice, a pump 23 capable of delivering a pressure of about p.s.i.gage, which is about the pressure delivered by the conventional airinjector pumps described above, has been found to operate veryeflectively. In this example, an average manifold vacuum of about inchesof mercury is realized in the chamber 63 and the same power output tothe master cylinder 77 was achieved with a booster unit generallysmaller than booster units utilizing only subatmospheric orsuperatmospheric pressure together with atmospheric pressure. Thisreduces the unit cost greatly and makes it considerably more compactwhich results in easier placement and repair of the unit 13. The pump 23is a conventional item on a number of present-day cars and is easilyplaced atop the engine 21 where it does not interfere with any of theother engine parts.

By the present invention, there has been provided a highly improved,more compact and less expensive power brake booster unit and while apreferred embodiment of the present invention has been illustrated anddescribed above in detail, various additions, substitutions,modifications and omissions may be made thereto without departing fromthe spirit of the invention as encompassed by the appended claims.

What is claimed is:

1. A fluid pressure operated servo motor for use in a braking system ofa motor vehicle, said servo motor comprising housing means, a movablewall supported within said housing means and dividing said housing meansinto first and second fluid chambers, means for continuously exposingsaid first fluid chamber to a subatmospheric pressure for tending tomove said wall in a first direction to decrease the volume of said firstchamber and to increase the volume of said second chamber, bypasspassage means interconnecting said first chamber with said secondchamber, normally opened bypass valve means for controlling the flowthrough said bypass passage means, means for moving said wall to anormal position when said bypass valve means is opened and when saidfirst chamber and said second chamber are both exposed to subatmosphericpressure, actuating passage means adapted to be connected to a source ofsuperatmospheric pressure and extending into said second fluid chamber,normally closed actuating valve means for controlling the fluidcommunication between said actuating passage means and said second fluidchamber, and operating means for simultaneously opening said actuatingvalve means and for closing said lbypass control valve means forexposing said second chamber to superatmospheric pressure while saidfirst chamber remains exposed to subatmospheric pressure for moving saidwall from its normal position.

2. The combination as recited in claim 1 wherein said pressureresponsive movable wall is operatively connected to a pressuredeveloping master cylinder adapted to pressurize vehicle brake cylinderswhereby movement of said actuating means in one direction developspressure in said master cylinder..

3. The combination recited in claim 1 wherein said pressure responsivemovable wall includes a piston body movable within said housing meansand said operating means includes a piston slidable within said pistonbody and wherein said bypass passage means and bypass valve means areformed between said piston and piston body.

4. The combination as recited in claim 3 wherein said movable wallcomprises a resilient diaphragm fixed at its outer end to said housingand seated at its inner end on said piston body.

5. The combination as recited in claim 1 wherein said actuatingpassagemeans includes a flexible conduit received in said second fluidchamber, one end of said flexible conduit being adapted to be exposed tosaid source of subatmospheric pressure, the other end of said flexibleconduit being afiixed to said movable Wall for movement with saidmovable wall.

6. The combination as recited in claim It wherein the means for movingsaid wall to its normal position comprises a flexible bellows receivedin said first fluid chamber and bearing against said wall and means forexposing the interior of said bellows to a source of atmosphericpressure.

'7. A fluid pressure operated servo motor as recited in claim 1 incombination with a motor vehicle having an internal combustion engine,and a system for supplying air to the exhaust system of said engine forfuither oxidation and dilution of the exhaust gases, said air supplyingsystem including an air compressor driven by said engine, said actuatingpassage means being connected to said air compressor.

References Cited UNITED STATES PATENTS 2,345,213 3/1944 OShei 602,373,272 4/1945 Stelzer 6010.5 XR 2,766,852 10/1956 Ingres 60--54.6 XR3,002,499 10/1961 Schultz 60-546 XR 3,094,844 6/1963 Helvern 60-54.63,237,525 3/1966 Stelzer 60-546 XR MARTIN P. SCHWADRON, PrimaryExaminer. ROBERT R. BUNEVICH, Examiner.

